At present, patients with tracheal intubation or tracheotomy cannot spit spontaneously. When patients have sputum, it is often necessary to suck the sputum out. It is also necessary to suck sputum from patients with lung infection when they have weak expectoration. Sputum suction tubes are commonly used when sucking sputum, which can suck sputum out of the body and solve the problem that patients may have sputum suffocation. However, it is necessary to find a specific location for sputum suction before suction is performed. Since the suction location is not visible, the sputum suction tube cannot accurately suck the sputum, which leads to the formation of sputum scabs. Prolonged stay of sputum scabs in the patients will bring great pain to the patients, wasting a lot of treatment time and even causing the patients to lose their lives.
Moreover, in the current circuit application of electronic medical instruments, the problem of switching between external signals and internal signals is often encountered, that is, when an external signal is input, the circuit automatically switches to the external signal; while when the signal is removed, the circuit automatically returns to an internal signal input state. A typical technical case is the switching between an internal MIC and an external MIC.
At present, there are several solutions for signal switching:
First, the switching is performed by a mechanical switching structure or is performed manually. However, both of these methods will lead to a limited service life of the mechanism and a low switching speed. Moreover, unnecessary noise interference will be introduced into the switching mechanism, which cannot be digitally controlled, and the contacts will easily oxidize.
Secondly, a relay is used for switching. The relay acts as a single-pole double-throw switch to switch the internal and external signals, which solves the problem of digital control. However, the volume of the circuit increases, the switching speed is not fast, and the contacts are also easy to oxidize.
Thirdly, an analog switch is used for switching, which acts as a single-pole and double-throw switch. However, the typical analog switch CD4053 has a minimum on-resistance of about 80 ohms. The on-resistance of the high-end analog switch MAX4887 is also about 5 ohms. The on-resistance is relatively large, which will seriously affect the communication distance when the analog switch is used on the communication line.
To sum up, there is an urgent need for a conversion circuit which has small resistance, high efficiency, stability and small interference, so as to improve the overall signal conversion quality and reduce the response time of electronic medical instruments, thereby improving the efficiency.
In view of the problems in the related art, no effective solution has been put forward by now.